SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d71001685e187d93184687daa6312d75bd7f354e608dd3cab1b099a5964ff40' 
  AND token = 'hKYrvtbDt5UNzk/MlNY0eLUQ09hS7IJBfOVgql1wTgw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}